Torque on the 335 FI motor makes it fun for everyday driving. The high spinning V8 of the M3 makes it a better track car, but harder to get the most out of the car in daily driving.

Do you prefer a FI I6 or a NA V8? That should be the big part of your choice. It's thing you can't really change after the purchase. The blown engine will give you better mpg, if that matters to you. V8s are unique in their own right, esp the sound.